Does more tin benefit HP expansion

[BJung]

I have lead ingots with 2% tin. Will adding more tin help a handgun HP expand while retaining the pedals?

[Meatpuppet]

I can't wait to see where this goes when the experts weigh in, because I have the same questions.

I think the real game changer is Powder Coating the boolit. If you have a proper bore fit, you can use soft alloy and guarantee proper expansion. Too much hardness can cause a bullet to be "brittle". Soft alloy and PC didn’t necessarily answer your question, but it effectively solved my problems. I generally use Rotometal's pure lead and toss a slug of Tin into the pot. I don't even know the percentages. It just works.

[mnewcomb59]

If you are using soft lead and losing the expanded part of the HP you are likely driving the bullet too fast. The best thing would be to use a shallower HP. If you add more tin it may control how fast the HP expands by making the HP walls harder, but it seems in my experience that a lot of tin allows the edges of the mushroom to slough off and become razor thin, then break off because it is so thin and weak. Purer lead will have the HP walls remain relatively thick and if they break off, they will break off in chunks rather than thin pieces of lead foil.

Also, I have seen where water jugs are really hard on a bullet, harder than actual flesh. Lately when my HPs appear to fragment in water jugs I test them in jugs again, but this time with 2 layers of denim to partially plug the HP. Bad guys aren't usually naked and deer are covered in thick fur. Many bullets that appear to be driven too fast in water jugs look just fine when a few layers of denim are put over the first jug.

[Mal Paso]

A Denim Jacketed Hollow Point?

Interesting, I'll have to try it.

[mehavey]

Tin is a flowing agent. Its effect on "hardness" is minimal.
Controlled expansion is usually obtained with a stronger jacket,
weakened in strategic points to permit reinforced peeling back w/o breaking soft interior chunks off.

Your best bet at handgun speeds is to stay soft -- to the point of PC'd pure lead if/as necessary

[fredj338]

Tin will help with pure lead, but hp design is more important. I mostly use 20-1 lead/tin for cup points to 1250fps or so. With 25-1, works well with deeper hp & softer lead running 850-1000fps. Pure lead with pc, maybe, just havent done any testing.

[truckjohn]

Tin makes lead harder, but also more brittle. The thing is, it takes a lot of tin to get the same hardness as wheel weight lead.

The tin/antimony/arsenic alloy used in wheel weights is a very good one, because it's not only hard, but somewhat flexible... Hollow points have a better chance of holding together, at least in theory...

In practice... A lot depends on the velocity and what it hits on the way in.

[dondiego]

Tin makes lead harder, but also more brittle. The thing is, it takes a lot of tin to get the same hardness as wheel weight lead.

The tin/antimony/arsenic alloy used in wheel weights is a very good one, because it's not only hard, but somewhat flexible... Hollow points have a better chance of holding together, at least in theory...

In practice... A lot depends on the velocity and what it hits on the way in.

Antimony, and often arsenic, makes a lead alloy brittle. Tin makes a lead alloy tougher and that is a good thing for hollowpoints. Wheel weights are a mixture of antimony, tin, and the majority lead. There are many instances here of WW being analyzed to show content percentages.

[fredj338]

Antimony, and often arsenic, makes a lead alloy brittle. Tin makes a lead alloy tougher and that is a good thing for hollowpoints. Wheel weights are a mixture of antimony, tin, and the majority lead. There are many instances here of WW being analyzed to show content percentages.

^THIS^^ LHP made with lead/tin are not as brittle as LHP made using lead & clip ww.

[Greg S]

I've been searching for the past few days but someone on this forum had done alot of tests concerning bullet expansion in a 38. I think he basically casted bullets from 40-1 to 16-1 and in-between then loaded them up and shot into 6" PVC filled with water.

[mehavey]

I was very surprised at this NIST publication on Alloy characteristics.

https://i.postimg.cc/9ffGc1DS/LEAD-TIN-Alloy.jpg
https://nvlpubs.nist.gov/nistpubs/jres/5/jresv5n5p1085_A2b.pdf

Can you guess why ?

[TurnipEaterDown]

The sudden drop in elongation % at 65/35, and recovery of elongation at 60/40 is surprising to me, but bullets don't usually contain that much tin so likely not what you are keying in on.
Probably the best thing to note is the Ductility (% elongation) Drop as the alloy goes from 0-5-10-15% tin which is countervailing to earlier statements.

Do keep in mind that this is a binary alloy. It is quite possible that alloys also containing antimony (3 part, I think Ternary) do respond respond differently.

[mehavey]

TurnipEater, this is NIST (Nat'l Institute of Stds) data. Pretty sure it's a clean binary Lead/Tin sample,
(which is good... since that's what we're trying to figure out)
:drinks:

No, what surprised me was the dip (then significant recovery) in tensile strength at 15% tin.
...and... NIST listing pure lead at BH=7
:!::?:

[TurnipEaterDown]

mehavey: Yes, agree.
What I meant was, maybe some earlier comments about tin increasing ductility is correct for a different alloy, such as a 3 part alloy. The data is for lead-tin, and I would believe it.

I would also believe that the table is based on fairly extensive testing (lead-tin alloys are what we used to use as solders, and electrical connections on PC boards and other joints do get engineered and do need parameters to have that done, especially for designs used in vibratory environments and such). Being an engineer, and seeing tensile tests performed, I understand some of this from my past.

The funny thing about laboratory tensile testing is that there are several ways to determine the point in test at which the data is reported. Gross Failure of the specimen, initiation of necking, microscopic cracking, etc. So, I think w/o knowing how the table was assembled, and seeing it's 32-27-33 at a point well above what we would usually use in a bullet (1-5% is a general range) then the engineer in me would walk past that. (20:1 in our speak is ~5% tin, probably most would say it is 5%, but if it's 20 parts lead and 1 part tin, the tin content in bulk is really 1/21.)

[popper]

Yes, at 20: or 10:1. IIRC an OP got real good expansion with HP 38 with 5:1.

[mnewcomb59]

For increasing hardness to control expansion I have found that tin and antimony in equal proportions is much better than adding a bunch of tin.

For example 1-1-98 and 20:1 are similar in hardness but the 20:1 in deep HP molds has thin, fragile hp walls and loses a small amount of weight from the HP walls thinning. Once the HP walls thin out they fold back sharply against the shank and either break off or lose the expansion. 1-1-98 will fold out and slightly back while keeping thick HP walls and pretty large expansion with 100% weight retention.

Likewise 2-2-96 has proven superior in faster, deep HP designs than any other alloy I have tried. The HPs mushroom nicely with thick walls and 100% weight retention.

I have also noticed that when I use my foundry type with ~2% copper by weight, the added copper affects HP expansion. The lead seems to work harden and the HPs that scratch with a fingernail, after expansion they don't scratch with a fingernail. These foundry type bullets mushroom out to about 90 degrees and do not curl backwards at all. There are no cracks or splits indicating antimony tin imbalance but they bend a certain amount, then harden and keep the hard wide mushroom. I estimate the copper ends up 0.1-0.2% by weight.

So I am replying again because I replied quick the first time and forgot to tell you to try some low amounts of antimony in your HP before trying the cup point like I recommended above. If you have WW try 50/50 or 1/3 WW and 2/3 soft lead. Then make sure your tin is at least equal to your antimony weight or slightly heavier.

1-1-98 is a far superior alloy for hollow points than 20:1 or 16:1 from my super serious and very scientific water jug testing of ~100 bullets in 5 years. It gets higher weight retention, better accuracy and larger expanded diameters.

Also, if your are a sprue plate tapper, like me, the low amounts of antimony in the lead make it cut so much nicer than binary lead tin alloys. I swear I had to tap 6-8 times to cut the sprues on a super hot mold with lead tin alloy the other day and it was driving me nuts.